The invention relates to patch bags made from polymeric blends, flexible films, and processes of making and using such bags and films. In particular the present invention relates to patch bags useful for packaging bone-in meats and other articles requiring bags which are heat shrinkable while having high resistance to puncture.
Various published patent documents disclose different types of patch bags, and polymer blends, flexible films, packaging and processes for making and/or using the same.
Known patch bags and patch bag structures are disclosed e.g. in U.S. Pat. Nos. 4,534,984; 4,755,403; 4,765,857; 4,770,731; 5,302,402; 5,376,394; 5,534,276; 5,540,646; 5,545,419; 5,645,913; and 6,004,599; and in Australian Application No. 88-11228 (filed Feb. 3, 1988 and published Aug. 4, 1988); and United Kingdom Application No. 2328930 (published Mar. 10, 1999). Film structures have also been disclosed which are relevant to bag formation such as in U.S. Pat. Nos. 4, 863,769; 5,403,668; 5,707,751; and 5,928,740.
Various commercial articles are known to exist in the art.
According to the present invention a novel polymeric blend comprising: 5 to 20 weight percent of (i) an ionomer polymer e.g. an ethylene-methacrylate acid copolymer whose acid groups have been neutralized partly or completely to forma salt, preferably a zinc or sodium salt; and 5 to 95 weight percent of (ii) a copolymer of ethylene and at least one C6 to C8 xcex1-olefin, wherein said copolymer (ii) has a melting point of from 55 to 95xc2x0 C., and a {overscore (M)}w/{overscore (M)}n of from 1.5 to 3.5; and optionally one or more of the following polymers:
0 to 90 weight percent of (iii) a copolymer of ethylene and at least one C4 to C8 xcex1-olefin, wherein said copolymer (iii) has a melting point of from 100 to 125xc2x0 C.;
0 to 90 weight percent of (iv) a copolymer of propylene and at least one monomer selected from the group of ethylene and butene-1, wherein said copolymer (iv) has a melting point of from 105 to 145xc2x0 C.; and
0 to 90 weight percent of (v) a copolymer of ethylene and at least one monomer selected from the group of hexene-1, octene-1 and decene-1, wherein said copolymer (v) has a melting point of from 125 to 135xc2x0 C. Preferably, polymers (ii), (iii), (iv), and (v) have a combined weight percentage of at least 80 weight percent based upon the total weight of these polymers.
A novel monolayer or multilayer film may be made of the foregoing blend, by casting, blowing, or by a trapped bubble technique. In one embodiment of the invention, a heat shrinkable film of the foregoing blend is produced, preferably having a total energy absorption of at least 1.2 Joule.
In another embodiment, the invention comprises: a patch bag made of a combination of: (a) a bag having an inside surface and an outside surface, made of a flexible, thermoplastic, biaxially stretched, heat shrinkable film having at least one layer comprising a blend of at least three copolymers comprising: 45 to 85 weight percent of a first polymer having a melting point of from 55 to 98xc2x0 C. comprising at least one copolymer of ethylene and at least one comonomer selected from the group of hexene-1 and octene-1; 5 to 35 weight percent of a second polymer having a melting point of from 115 to 128xc2x0 C. comprising at least one copolymer of ethylene and at least one xcex1-olefin; and 10 to 50 weight percent of a third polymer having a melting point of from 60 to 110xc2x0 C. comprising at least one unmodified or anhydride-modified copolymer of ethylene and a vinyl ester, acrylic acid, methacrylic acid, or an alkyl acrylate; where the first and second polymers above have a combined weight percentage of at least 50 weight percent based upon the total weight of the first, second and third polymers; and where the bag film has a total energy absorption of at least 0.70 Joule and a shrinkage value at 90xc2x0 C. of at least 50% in at least one of the machine and transverse directions; and (b) a patch film attached to at least one surface of the bag and covering at least 25% of the bag""s surface. This patch film comprises a flexible, thermoplastic film having at least one layer comprising a blend of at least two polymers comprising:
5 to 20 weight percent of (i) an ionomer polymer e.g. an ethylene-methacrylate acid copolymer whose acid groups have been neutralized partly or completely to forma salt, preferably a zinc or sodium salt;
5 to 95 weight percent of (ii) a copolymer of ethylene and at least one C6 to C8 xcex1-olefin, having a melting point of from 55 to 95xc2x0 C., and a {overscore (M)}w/{overscore (M)}n of from 1.5 to 3.5;
0 to 90 weight percent of (iii) a copolymer of ethylene and at least one C4 to C8 xcex1-olefin, having a melting point of from 100 to 125xc2x0 C.; and
0 to 90 weight percent of (iv) a copolymer of propylene and at least one monomer selected from the group of ethylene and butene-1, where the copolymer (iv) has a melting point of from 105 to 145xc2x0 C.;
0 to 90 weight percent of (v) a copolymer of ethylene and at least one monomer selected from the group of hexene-1, octene-1 and decene-1, where the copolymer (v) has a melting point of from 125 to 135xc2x0 C.; and polymers (ii), (iii), (iv), and (v) have a combined weight percentage of at least 80 weight percent based upon the total weight of polymers (i), (ii), (iii), (iv), and (v); and wherein the patch film has a total energy absorption of at least 1.2 Joule.
The invention is useful for packaging irregularly shaped objects having sharp projections such as bone-in cuts of meat.